Confirmation of the presence of the

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All articles available online at http://www.salamandra-journal.com

Correspondence

SALAMANDRA 49(1) 59–62 30 April 2013 ISSN 0036–3375

Confirmation of the presence of the

sphaerodactylid lizard Gonatodes vittatus in Guyana,

and an indication of a reproductively active population in Georgetown

Willem R. M. Meilink¹, Jonathan R. Clegg¹, Christopher J. Mayerl¹, Joana Sabino Pinto¹, Diana Grasso¹, Gwij Stegen¹, Maud Segal¹ & Philippe J. R. Kok^2,3

1) Master studies in herpetology, Vrije Universiteit Brussel, 2 Pleinlaan, B-1050 Brussels, Belgium

2) Biology Department, Unit of Ecology and Systematics, Vrije Universiteit Brussel, 2 Pleinlaan, B-1050 Brussels, Belgium

3) Department of Vertebrates, Royal Belgian Institute of Natural Sciences, 29 rue Vautier, B-1000 Brussels, Belgium Corresponding author: Philippe J. R. Kok, e-mail: Philippe.Kok@naturalsciences.be

Manuscript received: 15 March 2013

Introduced species can have potentially uncontrollable negative effects on ecological integrity and biodiversity (Lowe et al. 2000). They can disrupt locally established equilibria in a variety of ways, including competition, predation, and hybridisation (Mooney et al. 2001). The human-mediated introduction of species (e.g., by transport, see Kraus 2009) often has powerful, usually unintended consequences, and is considered a major cause of biodiversity loss (e.g., Sala et al. 2000, Olden et al. 2004, Clave- ro & García-Berthou 2005). Reliable data on the distribution and abundance of non-indigenous species are es- sential for an accurate assessment of their potential envi- ronmental impact.

The streaked clawed day gecko, Gonatodes vittatus (Lich tenstein, 1856) (Sphaerodactylidae), was origi- nally described from the central Venezuelan coast (La Guaira, Puerto Cabello, and Caracas; Lichtenstein 1856). In addition to coastal Venezuelan localities (Rivas et al. 2012), the species is known from northern Colombia, several Caribbean offshore islands along the Venezuelan coast, Trinidad, and Tobago (Murphy 1997, Gorzula &

Señaris 1999, Ugueto & Rivas 2010, Rivas et al. 2012) (Fig. 1). Identifying the exact native range of the species is difficult because part of its present distribution has probably resulted from introductions (as suggested by Mur- phy [1997] for Tobago). One introduced population in the Venezuelan interior (Bolívar state) apparently has been extirpated (Gorzula & Señaris 1999). The species appears to have been introduced into French Guiana, but even though no voucher specimen has as yet been mentioned, a photograph has been published (Anonymous 2010).

Cole et al. (2013) recently reported Gonatodes vitta- tus from Guyana, northern South America, on the basis of six museum specimens from two localities: Georgetown (capital city), and Rockstone Landing along the Essequi- bo river. Although not mentioned by Cole et al. (2013), these specimens apparently were collected more than 70 years ago, during the Terry-Holden British Guiana Ex- pedition of 1937–1938 (as stated in the catalogue of the Uni- versity of Michigan, Museum of Zoology, and confirmed by D. Dickey and D. Frost from the American Museum of Natural History [pers. comm.]). Cole et al. (2013) hypothesised a human-mediated introduction. No additional specimen has since been recorded from Guyana, and Cole et al. (2013) emphasized that the continued presence of the species needs confirmation.

We hereby document the rediscovery of Gonatodes vit- tatus in Guyana based on specimens collected in the urban area of Georgetown, the coastal capital city. Observations of an adult male and a juvenile (Fig. 2) suggest a reproductively active population. The apparent rarity of the species in Guyana and its localised geographic distribution sup- port the hypothesis of introduction by human-mediated transport.

Gonatodes vittatus is a small (snout–vent length [SVL]

ca. 35 mm) diurnal lizard that primarily inhabits beaches, thorn scrubland, forest edges, and deciduous, semi-deciduous, and premontane evergreen forests below 500 m a.s.l., as well as human habitations (Murphy 1997, Ugueto &

Rivas 2010). These lizards are sit-and-wait predators that feed primarily on insects, including mosquitoes, their lar- vae, and eggs, mostly depending on visual cues for prey detection (Persaud et al. 2003, Ugueto & Rivas 2010).

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Correspondence In their native habitat, they tend to prefer rough vertical

surfaces with cracks or crevices, such as small tree trunks (Demeter & Marcellini 1981). In urban areas, G. vittatus can occur on stonewalls, buildings, fences, and trash piles (Ugueto & Rivas 2010). The species is territorial, with males engaging in display behaviour and chasing away in- truding males and females doing the same to unfamiliar females (Stamps 1969, Ugueto & Rivas 2010).

Our specimens, an adult male and a juvenile, were collected on the front porch of a predominantly wooden house in Georgetown, Guyana (06°48’38’’ N, 58°08’57’’ W, 25 m a.s.l.) in the afternoon hours of 25 November 2012.

Both specimens will be deposited in the herpetological col- lections of the Royal Belgian Institute of Natural Sciences (export permits pending). The adult male (IRSNB 18303, 31.0 mm SVL) was moving about on a woven clothes basket in the corner of the porch, and the juvenile (IRSNB 18304, 16.8 mm SVL) was found soon after in the same spot.

Species identification is not in doubt and conforms to descriptions and photographs available in the literature (e.g., Murphy 1997, Ugueto & Rivas 2010). The male has a conspicuous white vertebral stripe bordered with slight- ly narrower black stripes, tapering posteriorly. These ex- tend from the snout to the base of the tail, which is missing.

Head and dorsum are yellowish orange. Flanks are bluish grey, limbs pinkish grey (Fig. 2). The juvenile is brown with

pale and dark round spots, and has a conspicuous white antehumeral stripe (Fig. 2).

The impact of Gonatodes vittatus on Guyana’s biodiversity is unknown. At present, the species appears to occur only in human-disturbed areas. In Georgetown, the species was found syntopically with Hemidactylus mabouia (Gekkonidae, another non-indigenous species, see below).

Although H. mabouia is nocturnal, competition between the two species has been reported from parts of the native range of G. vittatus. On Isla Margarita (Venezuela), for instance, G. vittatus is reported as declining, probably due to the increase in the numbers of introduced H. ma- bouia, which is now the dominant gecko species in most human habitations in the area (Ugueto & Rivas 2010).

Rivas et al. (2005) reported a similar decline in Caracas, mainland Venezuela, and hypothesised competition with, or even predation by, H. mabouia. The presence of H. ma- bouia could therefore be a limiting factor to the expansion of Gonatodes vittatus, which otherwise could be a success- ful invader in the urban area of Georgetown because its ecological niche is essentially unoccupied. Interestingly, a third non-indigenous species, the frog Eleutherodacty- lus johnstonei (Eleutherodactylidae), was observed in the garden of the same house where we observed G. vittatus and H. mabouia. The herpetofauna at this urban site is thus largely non-native.

Figure 1. Map of the known geographical distribution of Gonatodes vittatus. Dots represent major collecting localities. The red dot represents the type locality (La Guaira, Vargas state, Venezuela). Yellow dots represent the distribution in Guyana: (1) Georgetown;

(2) Rockstone Landing. The question mark refers to a putative record from French Guiana. Specimen localities were obtained from the literature (Murphy 1997, Anonymous 2010, Ugueto & Rivas 2010) and from the Global Biodiversity Information Facility (GBIF, http://www.gbif.org/).

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To date, four additional non-indigenous reptilian species (one turtle, three lizards) have been reported from Guyana:

Trachemys scripta (Emydidae). Native to the eastern and central United States of America, the species has been reported from Guyana by Lever (2006). Trachemys scripta was not reported from Guyana by Cole et al. (2013), and no voucher specimen seems to have been collected. The presence and exact distribution of this species in Guyana needs confirmation.

Basiliscus basiliscus (Corytophanidae). Native to the Pa- cific lowland forests of Central America and northwestern South America, B. basiliscus was reported from Guyana by Ávila-Pires (2005). The continued presence of a reproductively stable population needs to be confirmed (Ávi- la-Pires 2005, Cole et al. 2013) since no recent voucher speci men is available.

Anolis aeneus (Dactyloidae). Native to the Lesser An- tilles, this species was reported from Guyana by Under- wood (1964), and its presence confirmed by Cole et al.

Figure 2. Gonatodes vittatus from Georgetown, Guyana. (A) Adult male (IRSNB 18303, 31.0 mm SVL). (B) Juvenile (IRSNB 18304, 16.8 mm SVL). Photographs by P. J. R. Kok.

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Correspondence (2013) on the basis of numerous voucher specimens. We

observed a few individuals in the gardens of the George- town Zoo at the end of November 2012. Cole et al. (2013) suggested that “the taxonomic status of Anolis aeneus ver- sus Anolis extremus needs further investigation, both in areas where they occur in the West Indies and where they have been introduced on islands and the mainland of South America”.

Hemidactylus mabouia (Gekkonidae). Native to sub-Sa- haran Africa, H. mabouia was reported from Guyana by Kluge (1969). The presence of the species in Guyana has been formally confirmed by several authors (e.g., Ávila- Pires 2005, Cole et al. 2013) on the basis of numerous voucher specimens. We observed the species in George- town.

Herpetofaunal endemism in Guyana is estimated at 15%

(Cole et al. 2013), highlighting the importance of moni- toring introduced non-indigenous amphibians and reptiles in the country. However, the long-undocumented presence of Gonatodes vittatus in Guyana suggests a lack of such ef- forts.

Acknowledgements

These observations were made in the framework of the Field Herpetology course in Guyana provided to the second year stu- dents of Master in Herpetology at the Vrije Universiteit Brussel.

We thank D. Dickey and D. Frost (American Museum of Natu- ral History, New York) for information on museum specimens in their care, and R. Powell (Avila University, Kansas City) for valuable comments on an earlier version of the manuscript.

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